@article{fdi:010060545,
  title = {{N}itrogen transfers off {W}alvis {B}ay : a 3-{D} coupled physical/biogeochemical modeling approach in the {N}amibian upwelling system},
  author = {{G}utknecht, {E}. and {D}adou, {I}. and {M}archesiello, {P}atrick and {C}ambon, {G}ildas and {L}e {V}u, {B}. and {S}udre, {J}. and {G}arcon, {V}. and {M}achu, {E}ric and {R}ixen, {T}. and {K}ock, {A}. and {F}lohr, {A}. and {P}aulmier, {A}ur{\'e}lien and {L}avik, {G}.},
  editor = {},
  language = {{ENG}},
  abstract = {{E}astern boundary upwelling systems ({EBUS}) are regions of high primary production often associated with oxygen minimum zones ({OMZ}s). {T}hey represent key regions for the oceanic nitrogen ({N}) cycle. {B}y exporting organic matter ({OM}) and nutrients produced in the coastal region to the open ocean, {EBUS} can play an important role in sustaining primary production in subtropical gyres. {H}owever, losses of fixed inorganic {N} through denitrification and anammox processes take place in oxygen depleted environments such as {EBUS}, and can potentially mitigate the role of these regions as a source of {N} to the open ocean. {EBUS} can also represent a considerable source of nitrous oxide ({N}2{O}) to the atmosphere, affecting the atmospheric budget of {N}2{O}. {I}n this paper a 3-{D} coupled physical/biogeochemical model ({ROMS}/{B}io{EBUS}) is used to investigate the {N} budget in the {N}amibian upwelling system. {T}he main processes linked to {EBUS} and associated {OMZ}s are taken into account. {T}he study focuses on the northern part of the {B}enguela upwelling system ({BUS}), especially the {W}alvis {B}ay area (between 22 degrees {S} and 24 degrees {S}) where the {OMZ} is well developed. {F}luxes of {N} off the {W}alvis {B}ay area are estimated in order to understand and quantify (1) the total {N} offshore export from the upwelling area, representing a possible {N} source that sustains primary production in the {S}outh {A}tlantic subtropical gyre; (2) export production and subsequent losses of fixed {N} via denitrification and anammox under suboxic conditions ({O}-2 < 25 mmol {O}-2 m(-3)); and (3) the {N}2{O} emission to the atmosphere in the upwelling area. {I}n the mixed layer, the total {N} offshore export is estimated as 8.5+/-3.9x10(10) mol {N} yr(-1) at 10 degrees {E} off the {W}alvis {B}ay area, with a mesoscale contribution of 20 %. {E}xtrapolated to the whole {BUS}, the coastal {N} source for the subtropical gyre corresponds to 0.1+/-0.04 mol {N} m(-2) yr(-1). {T}his {N} flux represents a major source of {N} for the gyre compared with other {N} sources, and contributes 28% of the new primary production estimated for the {S}outh {A}tlantic subtropical gyre. {E}xport production (16.9+/-1.3x10(10) mol {N} yr(-1)) helps to maintain an {OMZ} off {N}amibia in which coupled nitrification, denitrification and anammox processes lead to losses of fixed {N} and {N}2{O} production. {H}owever, neither {N} losses (0.04+/-0.025x10(10) mol {N} yr(-1)) nor {N}2{O} emissions (0.03+/-0.002x10(10) mol {N} yr(-1)) significantly impact the main {N} exports of the {W}alvis {B}ay area. {T}he studied area does not significantly contribute to {N}2{O} emissions (0.5 to 2.7 %) compared to the global coastal upwelling emissions. {L}ocally produced {N}2{O} is mostly advected southward by the poleward undercurrent.},
  keywords = {{NAMIBIE} ; {OCEAN} {ATLANTIQUE} ; {ZONE} {TROPICALE}},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {10},
  numero = {6},
  pages = {4117--4135},
  ISSN = {1726-4170},
  year = {2013},
  DOI = {10.5194/bg-10-4117-2013},
  URL = {https://www.documentation.ird.fr/hor/fdi:010060545},
}